Bicycle tyres have been evolving into different areas. For use on a hard surface, such an asphalt covered metalled road, a relatively smooth tread pattern is desirable for improved speed and reduced noise and vibration. On the softer surfaces that are encountered off-road, such as soil and mud, a block tread pattern (i.e. a tread pattern with wide deep transverse channels that define protruding blocks or studs) is desirable, to allow the tyre to bite into the ground and provide improved traction.
Over time, some tyre manufacturers have tried to develop tyre treads that aim to combine both these features into a universal use tread pattern. Historically, this has been attempted by forming a single central rib in the tread which allows the tyre to run smoothly on harder surfaces and forming a block tread on each side of the central to allow limited cornering traction on soft surfaces.
This design of tyre with a single central rib was found to compromise the drive and brake traction on softer surfaces, or else it failed to deliver smooth quite performance on hard surfaces.